Many manufacturing processes require placement of identification tags on thin, elongate objects, such as wires, hoses and pipes. In complex communication and electric power distribution systems, individual wires within wiring harnesses must be correctly identified for proper connection of subsystems. Similarly, in hydraulic and pneumatic systems, hydraulic and pneumatic hoses and tubes also must be identified for correct coupling. Tags must be applied in a manner to identify individual objects with certainty, while not harming the object nor interfering with interconnection or function of the objects.
Conventional techniques for identifying individual conductors within wiring harnesses, such as those used in aircraft electrical systems, involve the placement of heat shrinkable, tubular identification sleeves over individual conductors, conductor-bundles, or cables. The tubular sleeving, commonly referred to as heat shrink tubing, is made of polymeric material that has been previously expanded and that, when heated, shrinks down to its original dimensions to form a tight fit around the object over which it has been placed. A length of conventional heat-shrink tubing is first marked by embossing or printing with identification indicia, such as numerals or letters. The marked tubing is then cut into individual pieces of a desired length, which are then individually threaded onto the object to be identified. Individual handling, marking and application of cut tubing is cumbersome and time-consuming.
An alternative type of conventional sleeve has been developed that is somewhat easier to mark with identification indicia. Two flat sheets of heat shrinkable material are periodically welded together along transverse lines to form a welded sheet of flat sleeves. The welded sheet can then be printed upon to place indicia on each sleeve. Individual sleeves are cut from the sheet prior to placement on wires or other objects to be identified.
Both heat-shrink tubing and flat welded sheets have the disadvantage of needing to be preprinted in advance with the identification indicia expected to be required for a particular manufacturing process. The individual operator then must select the correct preprinted sleeve corresponding to a particular wire to be identified. The requirement of preprinting and preparing individual sleeves is costly and time-consuming, and does not allow production flexibility with regard to changing identification requirements during a manufacturing run. Existing methods also do not enable printing on both sides of a piece of sleeving, as is sometimes desired, without turning over the sleeving.
An improved method for identifying objects is disclosed by U.S. Pat. No. 4,770,729, entitled "Method of Making a Welded Sleeve Identification" and assigned to the assignee of the current application. The method involves the printing of indicia on the leading end of a continuous strip of heat-shrinkable material, cutting indicia bearing pieces from the strip, and wrapping the pieces around an object to be identified. Each cut piece is gripped by a multiple joint arm and then moved to a position over top of the object to be identified, whereupon it is wrapped around the wire in a generally U-shaped configuration. The outwardly extending ends of the U-shaped pieces are then ultrasonically welded together adjacent the object to form a welded sleeve that can later be heat-shrunk into place. While this method represents a significant improvement over other prior art methods, the method has a disadvantage associated with handling the individual cut pieces of material and potential problems associated with mispositioning cut pieces when they are wrapped around the object to be identified.